X-radiation is a type of electromagnetic radiation that is generated by interactions of high energy electrons. Interactions of high energy electrons can be found in a natural environment or can be initiated artificially. Instruments purposefully used for X-radiation generating are generally called X-ray tubes.
While the release of energy in the form of X-radiation during an interaction of high energy electrons follows the laws of nature, the principle, based on which high energy electrons are prepared for the interaction in individual X-ray tubes, may differ.
Known X-ray tubes comprise electricity-powered X-ray tubes. This X-ray tube in its simplest version includes two electrodes, the cathode and the anode, that are installed in an air-tight glass bulb under reduced pressure. The electrodes are connected to a source of high voltage that provides the electrons emitted from the cathode and accelerated by the electric field between the electrodes with high energy. When such high energy electrons strike upon the anode, they penetrate its material. During such penetration the energy of the electrons is absorbed by the anode material and is subsequently released in the form of braking radiation whose components comprise X-radiation. The anode is designed in the form of a metal target that is usually square- or rectangular-shaped.
The disadvantages of standard X-ray tubes rest in the fact that the X-ray tubes must be connected to a source of high electric voltage. “In-situ” deployment of such X-ray tubes is considerably limited by this fact. Among other disadvantages is rather expensive manufacture and the fact that X-ray tubes are sensitive to rough handling that cannot always be eliminated in the field operations.
Among other X-ray tubes are so-called triboluminescence X-ray tubes. These X-ray tubes generate X-radiation by electrons that acquire the necessary high energy from triboluminescence. Triboluminescence is a physical phenomenon during which an electric charge is acquired by friction or crystal lattice deformation and the accumulated electric charge is discharged in the form of the transformation of high energy electrons. An example of the triboluminescent X-ray tube is, for example, the invention of a friction source of X-rays disclosed in the US 2013/0336460 A1 patent application (Carlos Camara, Mark G. Valentine). This invention deals with one of the major disadvantages of electrically powered X-ray tubes, namely dependence on the sources of high electric voltage. The X-ray tube according to the registered invention comprises a drive turning up a friction head. The friction head rubs a friction belt, which excites the triboluminescence effect. The friction head and friction belt are located in an environment with reduced pressure.
Common disadvantage of the aforementioned known X-ray tubes include the fact that if an object is put into the line of X-radiation, only one side the object is irradiated. If is it necessary to irradiate the object along the entire perimeter, the object must be rotated around the X-ray tube installed in a static way, or the X-ray tube must move around the statically installed object. Particularly, the method known as CT scanning and the subsequent reconstruction of a three-dimensional model of the object's internal structure requires a large set of X-ray images taken from many different angles. X-ray images are acquired by an X-radiation detector that is arranged behind the object if seen from the position of the X-ray tube and is situated in the line of the X-radiation coming out of the object. The need to move the X-ray tube—detector pair is demanding and requires expensive mechanical solutions. This reduces the speed of measurement and, moreover, the movement of the object or the X-ray tube introduces inaccuracies in the set of X-ray images that need to be compensated or otherwise compromise the quality of the resulting three-dimensional model. Therefore, it is desirable to minimize the rotational movement of the X-ray tube.
Minimization of such rotational movement is resolved, for example, by deployment of a group of X-ray tubes that are arranged around the object. An example of such a solution is disclosed in the US 2016/0166223 A1 patent application (Guy M. Besson). Although the aforementioned invention successfully resolves the rotational movement of the X-ray tube or the object, its disadvantages rest in the fact that its design requires a suitable supporting frame, is complicated and is suitable in particular for deployment in a static site. The invention utilizing a train of X-ray tubes requires a source of high voltage that is also difficult to convey.
The rotational movement of the X-ray tubes or the object is covered in the patent document U.S. Pat. No. 4,158,142 B (Jacob Haimson). The invention discloses a static X-ray tube that emits X-radiation that is led and swept on all sides of the object by means of electron optics. Electron optics accurately focuses the X-ray beam at any place along the entire perimeter of the irradiated object, which makes X-ray images from this instrument very accurate and measurements very fast. Disadvantages of this invention rest in particular in the fact that the acquisition costs of the electron optics are very high, the construction of the entire instrument is demanding and the presented instrument has a limited depth for inserting objects, which means that it is not suitable for elongated objects. Among other disadvantages is the fact that the presented instrument is not portable and is appropriate for static sites.
Although the requirements imposed by the method of CT scanning and the object internal structure three-dimensional model reconstruction are fulfilled by the aforementioned inventions to a great extent, there are still some disadvantages limiting a wide deployment of these known inventions. Such disadvantages include in particular high acquisition costs, requirements imposed on space and source of energy, spatial demands and necessity of gentle handling.
The task of the invention is the manufacture of a circular X-ray tube for the generation of X-radiation and of an X-ray instrument fitted with the circular X-ray tube to acquire X-ray images. Thanks to its design, the invention would make it possible to irradiate the object from all its sides, would be compact, easily portable, easily serviceable, would not require a source of high voltage and would be appropriate for use in X-ray instruments designed for deployment outside static sites, in particular in X-ray instruments designed for use in the field. The instrument according to the invention would not require full rotational movement by 360°, which would simplify its design to a great extent. The circular X-ray tube according to the invention would be more resistant to rough handling compared to the currently known X-ray tubes and its acquisition costs would be lower.